Automatic etcher for offset master

ABSTRACT

Apparatus for automatically applying etching solution to the surface of an offset master. The master is secured to the surface of a master cylinder. Etching solution is contained in an enlongated reservoir parallel to the master cylinder. A foam rubber feed roller is partially immersed in the etching solution and has a squeegee roller in contact with it. The feed roller is caused to step sequentially through three positions: a &#39;&#39;&#39;&#39;rest&#39;&#39;&#39;&#39; position in which it is withdrawn from the master cylinder and at rest with squeegee roller pressure relieved; a &#39;&#39;&#39;&#39;make ready&#39;&#39;&#39;&#39; position wherein it is rotating with the the squeegee roller bearing on it but still withdrawn from the master cylinder; and an &#39;&#39;&#39;&#39;etch&#39;&#39;&#39;&#39; position wherein it is in scrubbing contact with the master cylinder and rotating in the same direction as the master cylinder.

United States Patent 1 1 Ross et a1.

1 Nov. 5, 1974 1 AUTOMATIC ETCHER FOR OFFSET MASTER [75] Inventors: William A. Ross, Darien; Roderick N. Schmaling, Norwalk; Warren E. Olson, New Canaan, all of Conn.

I731 Assignee: Pitney-Bowes, 1nc., Stamford, Conn.

[22] Filed: Jan. 29, 1973 1211 Appl. No.: 327,509

Albert W. Scribner; Donald P. Walker [57] ABSTRACT Apparatus for automatically applying etching solution to the surface of an offset master. The master is secured to the surface of a master cylinder. Etching solution is contained in an enlongated reservoir parallel to the master cylinder. A foam rubber feed roller is partially immersed in the etching solution and has a squeegee roller in contact with it. The feed roller is caused to step sequentially through three positions: a rest position in which it is withdrawn from the master cylinder and at rest with squeegee roller pressure relieved; a make ready position wherein it is rotating with the the squeegee roller bearing on it but still withdrawn from the master cylinder; and an etch position wherein it is in scrubbing contact with the master cylinder and'rotating in the same direction as the master cylinder,

9 Claims, 7 Drawing Figures PATENTEUuuv 5 4914 3845713 SHEEI 3 BF 4 PATENTEU III]? 5 I974 SHEET L (If 4 FIG.7

1 AUTOMATIC ETCIIER FOR OFFSET MASTER BACKGROUND OF THE INVENTION sembly are supported within a housing H, most of which is omitted in order to expose the operative parts. In the following description, reference is made primar ily to the elements shown in FIG. 1. However, the ma- This invention relates to the etching of paper offset jority of these elements are duplicated on the opposite masters. This technique involves the use of a specially coated paper master carrying a toned image. An etching solution is applied which reacts with the coating. After etching, the image on the master is in the form of hydrophobic and hydrophilic regions. The master is thereafter employed in the usual manner for offset printing by applying a water solution and an oil based ink. The ink adheres only to the hydrophobic portion of the master and the resultant ink image is transferred by means of an offset blanket cylinder to the print stock.

It has been customary to etch such masters by submerging them completely in the etching solution. The master is fed through a bath of the solution, through a set of rollers, and out through a squeegee set of rollers. Submergence affects the physical characteristics of the paper, making it limp and difficult to handle, especially in an automated process. Accordingly, it is a primary object of this invention to provide apparatus for etching a paper master which avoids the submergence of the master in the etching solution. Other objects, features, and advantages will become apparent from the following description and appended claims.

SUMMARY OF THE INVENTION There is provided an apparatus for automatically applying an etching solution to an offset master which includes a master cylinder for supporting the offset master. An etching solution reservoir extends substantially parallel to the master cylinder. A feed roller also extends substantially parallel to the master cylinder and is partially immersed in the reservoir. A squeegee is in engagement with the feed roller. Means are provided for rotating the feed roller and means are provided for positioning the feed roller in a first position out of engagement with the master cylinder and a second position in engagement with the master cylinder.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is an isometric view of an apparatus constructed in accordance with this invention;

FIG. 2 is an enlarged cross section taken along the line 22 of FIG. 1;

FIG. 3 is a partial isometric view taken from the opposite side of FIG. 1 to illustrate otherwise hidden elements;

FIG. 4 is a side view showing the apparatus in the rest position;

FIG. 5 is a view similar to FIG. 4 showing the apparatus in the make ready position;

FIG. 6 is a view similar to FIGS. 4 and 5 showing the apparatus in the etch position; and

FIG. 7 is an enlarged cross sectional view illustrating the feed roller construction.

DESCRIPTION OF THE PREFERRED EMBODIMENT There is illustrated in FIG. 1 apparatus in accordance with the present invention for applying etch solution to the surface of an offset master. The master is mounted on the periphery of a master cylinder 10. The master cylinder 10 and the various elements of the etching asside of the apparatus. Where these are illustrated (as in FIG. 3), they are given similar reference numerals but with a prime attached.

Extending parallel to, and near the bottom of, master cylinder 10 is an etching solution reservoir 12. Secured to the housing by means of a pivot M at each end of the assembly is a lever arm 16. Theend of lever arm 16 nearest the master cylinder defines a slot 18 which slidably receives the pin 20, mounted in one corner of a substantially triangularly shaped camming plate 22. Another corner of the camming plate is pivoted on a shaft 24 mounted on the housing. Camming. plate 22 rotatably supports the stub shaft 26 of a gear 30. As will be seen by reference to FIG. 7, foam roller 28 comprises a rigid cylinder 29 covered by a foam sleeve 31. A recess 33 in the end of the cylinder receives a disc 35 which is made non-rotatable with respect to the cylinder by means of a key 37. The disc 35, in turn, is recessed to receive an end cap 39 having a pair of diametric keys 39a, 3%, a central post 41 extending through the disc 35, and an external hub 43 defining a central opening with a keyway 45. End cap 39 is urged outwardly by means of an internal spring 47 but is retained in disc 35 by a circular retainer 49. The stub shaft 26 carries a post 51 and key 53 sized to engage the keyway 45. By means of this construction, foam roller 28 is easily removable by pressing in the end cap 39 to disengage keyway 45 from key 53. The feed roller 28 extends parallel to the master cylinder 10 and the lower portion of its foam rubber sleeve 31 is immersed in the etching solution contained in reservoir 12. The gear 30 is driven by a pinion 32 which is driven in turn by a motor 34, pulleys 36 and 38, and belt 40.

The end of lever arm 16 farthest from the master cylinder 10 is connected to a pin 42 in the lower end of a link assembly 44. Link assembly 44 comprises a first planar link member 46 having an outwardly extending tab 48 and an upwardly extending tongue 50. The body of first link member 46 defines a vertical slot 52. The link assembly 44 also comprises a second planar-link member 54 which is substantially L-shaped and includes a tab 56 substantially parallel to tab 48. The tab 56 also defines a slot 58 slidably receiving the tongue 50. Extending between the tabs 56 and 48 is an adjusting screw 60 and compression spring 62.

Extending across the apparatus and parallel to the feed roller 28 is a rotatable control shaft 64 which has mounted in its end eccentric pin 66 which extends rotatably through an opening in the second link member 54 and the slot 52 in link member 46. The control shaft 64 is driven by belt 68 from motor 70. The control shaft 64 is milled to provide depressions 72 (FIG. 2) spaced axially and radially around the shaft. Suitable brackets 74 mounted on housing H support switches 76, 78 and 80 adjacent the control shaft 64. The actuator buttons 82 of these switches are positioned to engage respective depressions 72.

Also mounted by pivot 14 on the housing is a support arm 84 which, at one end, rotatably supports the shaft 86 of an acetyl squeegee roller 88 which engages the feed roller 28. The other end of the support arm 84 carries a tab 90 which engages an adjusting screw 92 carried by the housing. Tab 90 is maintained in engagement with screw 92 by means of tension spring 94 extending between the housing and the end of support arm 84.

Reference to FIG. 3 will disclose a solenoid 96 coupled by means of a wire 98 to a sector gear 100. Sector gear 100 is rotatable about a pivot 102 and is normally retained in its illustrated position by means of a tension spring 104. Sector gear 100 engages a pinion 106 secured to a shaft 108 which carries an elastomeric wiper blade 110 extending the length of the master cylinder 10.

OPERATION The illustrated apparatus is controlled by a master sequencer (not shown) in conjunction with the switches 76, 78, 80. It assumes three positions which are illustrated in FIGS. 4, 5, and 6. FIG. 4 is the rest position. In this position, the feed roller 28 is withdrawn from both the master cylinder 10 and squeegee roller 88 to prevent temporary indentation of the foam by the squeegee and its lower portion is submerged in the etching fluid. If the etching apparatus has been sitting idle for any length of time, the feed roller 28 may be partially dried out. Also, the etching fluid has a tendency to crystallize, forming hard but resoluble crystals on the surface of the roller.

Upon actuation of the master sequencer, both motors 34 and 70 are activated. Motor 34 begins to rotate the feed roller 28 through the belt 40 and gears 32 and 30. At the same time, the control shaft 64 begins to rotate from motor 70 and belt 68. This causes eccentric pin 66 to move in a counterclockwise direction, as illustrated in FIG. 4. This moves the link assembly 44 downwardly, rocking lever arm 16 in a counterclockwise direction lifting camming plate 22 upwardly and clockwise about shaft 24. This carries the feed roller 28 into engagement with squeegee roller 88 and closer to the master cylinder 10 to the position illustrated in FIG. 5. In moving to this position, the gear 30 rolls around the periphery of pinion 32 and both the pinion and the gear continue their rotation. When the make ready position, illustrated in FIG. 5, has been reached, switch 76 stops the motor 70. While in this position, the feed roller 28 is rolling in the solution and is simultaneously being squeegeed by squeegeeroller 88 to redissolve any crystals, to redistribute the fluid evenly on the surface of the roller, and to scavenge any remaining ink from the feed roller 28.

After a sufficient period of time, for example to 6 seconds, the master sequencer once again actuates motor 70. The eccentric pin 66 now moves downwardly to the position illustrated in FIG. 6, rocking the lever arm 16 further counterclockwise and raising the feed roller 28 into contact with the master on master cylinder while simultaneously maintaining contact with squeegee roller 88 which is lifted against the force of spring 94. It will be noted that the rotation of feed roller 28 is in the same direction as that of the master cylinder 10, as a result of which the oppositely disposed portions of the peripheries, or surfaces, of the feed roller 28 and master cylinder 10, are respectively moving in opposite directions to one another, as indicated by the arrows in FIG. 5. Accordingly, in the areas of engagement with one another the direction of movement of the surface of the feed roller is opposite to the direction of movement of the surface of the master cylinder 10, as illustrated in FIG. 6. This creates a scrubbing action which improves the etching quality. Fresh etch solution is pumped continuously into reservoir 12 from a remote tank. It flows over a dam which maintains the proper fluid level for the feed roller.

The feed roller 28 remains in the etch" position for several revolutions of the master cylinder. The master sequencer then once again actuates motor to rotate control shaft 64 and, through link assembly 44, the feed roller 28 back to the rest position of FIG. 4. When this position is reached, the switch shuts off the motor 70 and also the motor 34.

The sequencer now operates solenoid 96 which retracts wire 98 and rotates sector gear 100 in a clockwise direction as viewed in FIG. 3. This rotates pinion 106 and wiper blade 110 in a counterclockwise direction to wipe the remaining fluid off the surface of the master, causing the fluid to run back into reservoir 12. Solenoid 96 is then deactivated and the wiper blade is returned by spring 104.

Two adjustments are provided for achieving the proper resiliency and positioning of the respective parts. One such adjustment is the adjusting screw 60 contained in the link assembly 44. As previously explained, the second link member 54 is constrained to move with the eccentric pin 66. Adjustment of screw 60 extends or shortens the overall length of the link assembly 44 by sliding the first link member 46 relative thereto. This rotates the lever arm 16 and thereby varies the pressure of feed roller 28 against master cylinder 10. The presence of spring 62 provides the required degree of resiliency.

A second adjustment is provided by adjusting screw 92 shown in FIG. 1. This screw raises or lowers the end of support arm 84 against the tension of spring 94 to vary the pressure of the squeegee roller 88 against feed roller 28. Both adjustments are duplicated at the opposite end of the assembly.

It will be noted that the invention described above is a completely modular unit. It can be independently subassembled. As it has its own motor, it can be powered for adjustments and test outside of, and independent from, any machine with which it is used. It is easily removed as a unit for service and cleaning.

It is believed that the many advantages of this invention will now be apparent to those skilled in the art. It will also be apparent that a number of variations and modifications may be made in this invention without departing from its spirit and scope. Accordingly, the foregoing description is to be construed as illustrative only, rather than limiting. This invention is limited only by the scope of the following claims.

We claim:

1. Apparatus for automatically applying an etching solution to an offset master which comprises: a rotatable master cylinder for supporting the offset master; means for rotating the master cylinder; an elongated reservoir for etching solution; said reservoir extending substantially parallel to said master cylinder; a rotatable feed roller extending substantially parallel to said master cylinder; means for rotating said feed roller partially immersed in etching solution in said reservoir; squeegee means engageable with said feed roller; and automatic control means for sequentially positioning said feed roller in three discrete positions including a make ready position wherein said rotating feed roller is disposed in engagement with said squeegee means but out of engagement with said master cylinder; then in an etching solution application position wherein said rotating feed roller is disposed in engagement with both said squeegee means and said rotating master cylinder and then in a rest position wherein said feed roller is disposed out of engagement with both said squeegee means and said master cylinder.

2. The apparatus of claim 1 wherein said control means comprises: lever means adapted to be moved for raising and lowering said feed roller, a rotatable control shaft having an eccentric pin extending therefrom, and link means including a link interconnecting said control shaft pin and said lever means, said control shaft being rotatable for moving said interconnecting link and thus said lever means for raising and lowering said feed roller.

3. The apparatus of claim 2 including said offset master supported by said master cylinder and wherein the link means includes means for adjusting the working length of said link for varying the pressure with which the feed roller engages the offset master as supported by said master cylinder.

4. The apparatus of claim ll wherein the engaged portions of the respective surfaces of said rotating feed roller and offset master cylinder move in directions which are opposite to one another.

5. The apparatus of claim 1 wherein said means for rotating said feed roller comprises a driven gear connected to said feed roller, and a driving gear meshing with said driven gear and rotatable about an axis; and wherein said positioning means comprises means for moving said feed roller and driven gear about said axis.

6. The apparatus of claim 1 wherein said squeegee means comprises a squeegee roller and means disposing said squeegee roller for engagement by said feed roller.

7. The apparatus of claim 6 wherein said squeegee roller disposing means comprises: a pivoted support arm carrying said squeegee roller at a first end thereof, spring means for urging said support arm in a direction to resiliently hold said engaged squeegee roller in Contact with said feed roller, and adjustable stop means for limiting movement of said support arm and for varying the pressure of the squeegee roller against the engaged feed roller.

8. The apparatus of claim 1 further comprising: means for wiping excess etching solution from the offset master as supported by said master cylinder; said wiping means including an elastomeric wiping blade disposed parallel to said master cylinder and out of contact therewith, and means for rotating said wiping blade to a wiping position wherein said wiper is disposed in contact with said master cylinder.

9. The apparatus of claim 8 wherein said feed roller has opposed ends and includes a spring-loaded hub at at least one end thereof, said hub being normally rotatably engaged by said feed roller rotating means, and said hub being movable against the spring-loading thereof for disengagement from said feed roller rotating means. 

1. Apparatus for automatically applying an etching solution to an offset master which comprises: a rotatable master cylinder for supporting the offset master; means for rotating the master cylinder; an elongated reservoir for etching solution; said reservoir extending substantially parallel to said master cylinder; a rotatable feed roller extending substantially parallel to said master cylinder; means for rotating said feed roller partially immersed in etching solution in said reservoir; squeegee means engageable with said feed roller; and automatic control means for sequentially positioning said feed roller in three discrete positions including a make ready position wherein said rotating feed roller is disposed in engagement with said squeegee means but out of engagement with said master cylinder; then in an etching solution application position wherein said rotating feed roller is disposed in engagement with both said squeegee means and said rotating master cylinder and then in a rest position wherein said feed roller is disposed out of engagement with both said squeegee means and said master cylinder.
 2. The apparatus of claim 1 wherein said control means comprises: lever means adapted to be moved for raising and lowering said feed roller, a rotatable control shaft having an eccentric pin extending therefrom, and link means including a link interconnecting said control shaft pin and said lever means, said control shaft being rotatable for moving said interconnecting link and thus said lever means for raising and lowering said feed roller.
 3. The apparatus of claim 2 including said offset master supported by said master cylinder and wherein the link means includes means for adjusting the working length of said link for varying the pressure with which the feed roller engages the offset master as supported by said master cylinder.
 4. The apparatus of claim 1 wherein the engaged portions of the respective surfaces of said rotating feed roller and offset master cylinder move in directions which are opposite to one another.
 5. The apparatus of claim 1 wherein said means for rotating said feed roller comprises a driven gear connected to said feed roller, and a driving gear meshing with said driven gear and rotatable about an axis; and wherein said positioning means comprises means for moving said feed roller and driven gear about said axis.
 6. The apparatus of claim 1 wherein said squeegee means comprises a squeegee roller and means disposing said squeegee roller for engagement by said feed roller.
 7. The apparatus of claim 6 wherein said squeegee roller disposing means comprises: a pivoted support arm carrying said squeegee roller at a first end thereof, spring means for urging said support arm in a direction to resiliently hold said engaged squeegee roller in contact with said feed roller, and adjustable stop means for limiting movement of said support arm and for varying the pressure of the squeegee roller against the engaged feed roller.
 8. The apparatus of claim 1 further comprising: means for wiping excess etching solution from the offset master as supported by said master cylinder; said wiping means including an elastomeric wiping blade disposed parallel to said master cylinder and out of contact therewith, and means for rotating said wiping blade to a wiping position wherein said wiper is disposed in contact with said master cylinder.
 9. The apparatus of claim 8 wherein said feed roller has opposed ends and includes a spring-loaded hub at at least one end thereof, said hub being normally rotatably engaged by said feed roller rotating means, and said hub being movable against the spring-loading thereof for disengagement from said feed roller rotating means. 